Sensors are used in a wide-ranging technical environment. Thus, for example, particularly in automation and processing technology, sensors are currently used for measuring process parameters such as fill level, pressure, temperature, etc. Actuators, such as valves, heating elements, or the like are used to influence the process parameters. According to the related art, the measured values determined by the sensors are analyzed by a process control system and the actuators are activated in order to be able to have the process run in the predefined process window. Since the sensors are often positioned at points of a manufacturing facility which are widely separated in space, wire-bound communication of the sensors with the process control system and with control and display units is often connected with a high cost outlay.
As a result of this, efforts have been undertaken to implement the communication of the sensors with the process control system and with control and display units wirelessly, on the basis of the Bluetooth standard, for example. DE 100 32 774 A1 describes a system in which field devices are wirelessly connected to a control and display unit for data input and display for process automation. According to this publication, the control and display unit is implemented as a separate portable unit. Furthermore, this publication discloses that the wireless connection is produced in accordance with the Bluetooth standard. According to one embodiment of DE 100 32 774 A1 cited, the field devices of a processing facility are exclusively connected wirelessly to a junction, which is linked via a data bus to the process control system. As a result, the field devices transmit the current measured values wirelessly to the process control system, which in turn activates the different actuators on the basis of the measured values.
A system for wireless information transmission for multiple sensors and/or actuators on a machine is known from DE 199 33 814 A1. The known system comprises multiple users such as sensors or actuators and a base station. The base station preferably emits a broadband high-frequency signal produced according to the DSSS method. The users are located at different distances from the base station. The users code the high-frequency signal received according to the SDMA method, modulate it, and reflect it back to the base station. Signal correlation and demodulation is performed in the base station.
The field devices or sensor units known from the related art have the disadvantage that each sensor unit is equipped with a processor which must assume both the tasks of controlling measured signal receivers, A/D converters, and interfaces, and also processing the measured signal. Processors which may assume these tasks are costly to provide and operate.